Long-Term Debt (Details) (USD $)	9 Months Ended				0 Months Ended	1 Months Ended		9 Months Ended		0 Months Ended		1 Months Ended		9 Months Ended	1 Months Ended					1 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013		Jul. 15, 2014 Convertible Subordinated Notes Due 2023	Jun. 30, 2013 Convertible Subordinated Notes Due 2023	Jan. 31, 2013 Convertible Subordinated Notes Due 2023	Sep. 30, 2014 Convertible Subordinated Notes Due 2023	Dec. 31, 2013 Convertible Subordinated Notes Due 2023	Jul. 15, 2014 Convertible Subordinated Notes Due 2023 Common stock	Jul. 15, 2014 Convertible Subordinated Notes Due 2023 Common stock	Jun. 30, 2013 Convertible Subordinated Notes Due 2023 Privately-negotiated capped call option	Jan. 31, 2013 Convertible Subordinated Notes Due 2023 Privately-negotiated capped call option item	Sep. 30, 2014 Convertible Subordinated Notes Due 2023 Privately-negotiated capped call option	Jan. 31, 2013 Convertible Subordinated Notes Due 2023 Stock prices below $27.79 per share Maximum	Jan. 31, 2013 Convertible Subordinated Notes Due 2023 Stock prices below $27.79 per share Minimum	Jan. 31, 2013 Convertible Subordinated Notes Due 2023 Stock prices above $38.00 per share	Sep. 30, 2014 9% fixed rate term notes due 2029	Dec. 31, 2013 9% fixed rate term notes due 2029	Apr. 30, 2014 9% fixed rate term notes due 2029 GSK	Sep. 30, 2014 9% fixed rate term notes due 2029 GSK Collection Account	Sep. 30, 2014 9% fixed rate term notes due 2029 GSK Milestone Reserve Account	Apr. 30, 2014 9% fixed rate term notes due 2029 GSK Milestone Reserve Account
Debt disclosures
Convertible Subordinated Notes due 2023	$ 255,109,000		$ 287,500,000	[1]				$ 255,109,000	$ 287,500,000
Non-Recourse Notes Payable due 2029	450,000,000		0	[1]														450,000,000	0
Long-term Debt	705,109,000		287,500,000
Loan amount							287,500,000													450,000,000
Proceeds from issuance of debt, net of issuance costs	434,677,000	281,622,000					281,200,000													434,700,000
Payments for capped call options													36,800,000
Number of derivative instruments purchased													2
Interest rate (as a percent)								2.125%												9.00%
Conversion rate of shares						46.9087	35.9903	47.4323
Conversion price of convertible notes into common stock (in dollars per share)						$ 21.32	$ 27.79	$ 21.08			$ 21.32
Percentage of principal amount at which the entity may be forced to redeem some or all notes as a result of a fundamental change (as defined)							100.00%
Strike price for the underlying number of shares (in dollars per share)												$ 21.32	$ 27.79	$ 21.08
Cap price for the underlying number of shares (in dollars per share)												29.16	38.00	28.83
Net shares settlement payable to the entity															2,779,659	0
Incremental anti-dilutive benefit (in shares)																	0
Percentage of royalties from global net sales																				40.00%
Balance of segregated bank account classified as current restricted cash	5,600,000		0	[1]																	1,600,000	4,000,000	32,000,000
Reserve account for covering remaining milestone payments as a percentage of future milestone payments																				40.00%
Transaction costs																				$ 15,300,000
Number of common shares issued upon debt conversion					149,645					1,519,402

[1] Condensed consolidated balance sheet at December 31, 2013 has been derived from audited consolidated financial statements.